Bench mark AHB2 Black Instruction manual

Benchmark

AHB2

Instruction Manual

Reference Stereo Power Amplifier

100W/channel into 8-Ohms

380W bridged mono into 8-Ohms

Contents

Introduction

Product Overview

True HRA Performance

Virtually Noise Free

Virtually Distortion Free

Patent Information

Licensed THX Patents

Important Safety Instructions

Safety Symbols

Safety Precautions

Front Panel

Front Panel Layout

Rear Panel

Rear Panel Layout

Quick Start Guide

Overview

1. Set the MODE Switch

2. Set the SENSITIVITY Switch

3. Connect the Audio Inputs

4. Connect the Speaker Outputs

5. Connect the AC Power Cord

6. Turn on the Power

7. Check the Status Indicators

Bidirectional 12 Volt Trigger

Linking Multiple Audio Components

Trigger Wiring

Trigger Cables

Automatic Power-Down Feature

40 Minute Timer

Timer Deactivates the 12V TRIGGER

No Warm-Up Required

AUTO-ON Feature

Rack Mounting

Rack Mount Option

Rack Mounting Instructions

8

8

9

9

9

9

10

10

11

11

11

12

12

12

12

12

12

12

13

13

14

14

14

3

3

3

4

4

5

7

7

3

3

3

3

Fault Protection Circuitry 15

Fault-Detection Circuits 15

PROTECT Mode (Both MUTE Lights On) 15

PROTECT Mode - Fault Codes

Clipping Fault

Over-Current Fault

SOA Fault

Over-Temperature Fault

Power Supply Fault

16

17

18

19

20

21

Specifications

Rated Output Power

Output Current

Output Voltage

Frequency Response

Signal to Noise Ratio

Distortion

Crosstalk

Input Sensitivity

Input Impedance

Input CMRR

Trigger I/O

Damping Factor

Environmental

Mechanical Drawings

Dimensions

Rack-Mount Dimensions

22

22

22

22

22

22

22

23

23

23

23

23

23

23

24

24

25

Performance Plots 26

Regulatory Compliance 31

FCC and RoHS Compliance Statements 31

FCC Notice (U.S. Only)

RoHS Compliant Information

CE Certificate of Conformity

Safety

31

31

32

33

Warranty Information 34

Benchmark 1-Year Warranty 34

Benchmark Extended Warranty Options 35

Notes on Warranty Repairs 35

Consignes de Sécurité Importantes

(French)

Symboles de Sécurité

Mesures de Sécurité

36

36

37

Appendix 39

A Radical Approach to Power Amplification

39

AHB2

Instruction Manual Rev G Page 2

Introduction

Thank you for purchasing the Benchmark

AHB2

audio power amplifier. To take full advantage of the extraordinary performance of this amplifier, and to enjoy long and trouble-free use, please read this manual carefully.

Product Overview

True HRA Performance

The

AHB2

is a reference-grade audio power amplifier that is specifically designed to complement the performance delivered by the finest High Resolution Audio (HRA) recording and playback systems. The SNR and THD performance of the

AHB2

put this amplifier in a class by itself.

Virtually Noise Free

The

AHB2

delivers a SNR that exceeds 132 dB A-weighted. This makes the

AHB2

15 to 30 dB quieter than most top-quality power amplifiers. 132 dB is approximately equivalent to the noise performance of a perfect 22-bit digital system.

Virtually Distortion Free

A THX-patented feed-forward error correction system virtually eliminates all traces of distortion at all signal level and loading conditions. The

AHB2

shows no traces of the crossover distortion that can occur when push-pull outputs stages switch between output devices. Without crossover distortion, low-level details are resolved with precision. At high output levels, the

AHB2

remains virtually distortion free while driving heavy loads.

Patent Information

The

AHB2

incorporates patented

THX® Achromatic™ Audio Amplifier Technology (THX

AAA™

) which is licensed from THX Limited.

Licensed THX Patents

 U.S. Patent No. 8,004,355

 U.S. Patent No. 8,421,531

 Mexico Pat. No. 312399

 Mexico Pat. No. 317696

 Canada Pat. No. 2753575

 S. Korea Pat. No. 10-1429804

 Additional Patents Pending

A complete list of applicable patents is available at: http://patents.thx.com/abc/

AHB2


Important Safety Instructions

Safety Symbols

This symbol alerts the user that there are important operating and maintenance instructions in the literature accompanying this appliance.

This symbol alerts the user to the presence of uninsulated voltages within the unit that can cause dangerous electric shocks.

This symbol alerts the user to the presence of voltages at the output connectors that can cause dangerous electric shocks.

This symbol alerts the user that the product can only be used safely at altitudes lower than

2,000 meters.

This symbol alerts the user that the product can only be used safely in non-tropical climates.

AHB2


Safety Precautions

Important Operating and Maintenance Instructions

1.

Read these instructions.

2.

Keep these instructions.

3.

Heed all warnings.

4.

Do not use this apparatus near water.

5.

Do not spray any liquid onto any surface, as this may cause a dangerous condition. Clean only with a damp cloth.

6.

This apparatus produces heat when operated normally. Operate in a well-ventilated area. Do not block the heat-sink fins located on either side of the unit. These emit heat and must be well ventilated.

7.

Do not install near any heat sources such as radiators, heat registers, stoves or other apparatus that produce heat.

8.

Use only with attachments and accessories specified by the manufacturer.

9.

Use only with a stand, rack, or table designed to support the weight of this apparatus. Make sure that injury or damage will not result from cables pulling on the apparatus or its mounting.

Speaker Output Voltage Warning

10.

The speaker outputs are capable of producing dangerous voltages. Use insulated speaker connections. Unplug the apparatus before making changes to the speaker output connections.

Hazardous Internal Voltage Warnings

11.

Refer all servicing to qualified service personnel. There are no user-serviceable parts inside the unit. There are exposed high voltages inside the unit and these may persist after the unit is unplugged. Do not attempt to open any of the covers, and do not remove any fasteners.

Opening the unit will void the warranty.

12.

Certain parts are safety related, or are required to meet certain regulations. All parts must be replaced with exact replacements unless written approval is granted by Benchmark.

Unauthorized substitutions and modifications can create unsafe or non-compliant operating conditions and will void the warranty. Unauthorized modifications may cause fire and shock hazards. Unauthorized modification may cause the unit to emit excessive radio and magnetic interference. Modifications may reduce the immunity to external interference. Do not refer servicing to personnel who offer product modification services.

AHB2


Line Cord and Fuse Warnings

13.

The AC line cord is removable. Use a grounded 3-prong line cord that is appropriate for your region. Your dealer can provide you with the correct line cord.

14.

Do not defeat the purpose of the grounded power plug. The ground prong is provided for your safety. When a 3-prong outlet is not available, please consult an electrician for replacement of the obsolete outlet. Do not use 2-prong to 3-prong adapters. Do not attempt to solve AC hum problems by lifting the AC safety ground!

15.

Unplug this apparatus during lightning storms or when unused for long periods of time.

16.

This apparatus is equipped with an auto-ranging power supply. There is no internal voltage selection switch - do not attempt to open the unit. Operating voltage ranges are 100 to 120 Vac

+/- 10%, and 220 to 240 Vac +/- 10%. Operating frequency is 50 to 60 Hz. All operating voltages use the same fuse size.

17.

For continued fire and shock protection always replace the fuses with the correct size and type

(T 8A H 250V, 5x20mm), (T = time lag, 8A = eight Amps, H = high breaking capacity, 250V = voltage rating, 5x20mm = cartridge size). High-breaking fuses use a ceramic body. Use Bel

Fuse 5HT 8-R, or Schurter 0001.2513, or an exact equivalent. The fuse drawer includes two fuses. Always replace both fuses at the same time.

Operating Environment Warnings

18.

This product can only be used safely at altitudes lower than 2,000 meters.

19.

This product can only be used safely in non-tropical climates.

AHB2


Front Panel

Front Panel Layout

Left to Right:

 Power Switch

 Power Indicator

 Channel 1 Clip Indicator

 Channel 1 Temperature and High-Current Indicator

 Channel 1 Mute Indicator

 Channel 2 Mute Indicator

 Channel 2 Temperature and High-Current Indicator

 Channel 2 Clip Indicator

AHB2


Rear Panel

Rear Panel Layout

Top Row, Left to Right:

 Channel 2 Speaker Binding Posts

 AC Power Entry with Fuse Drawer

 Channel 1 Speaker Binding Posts

Bottom Row, Left to Right:

 12 Volt Trigger Input / Output Connector

 3-Position Sensitivity Switch - Sets Gain

 Balanced XLR Input for Channel 2

 NL4 Speaker Output for Channel 2

 NL4 Speaker Output for Bridged Mono Operation

 NL4 Speaker Output for Channel 1, or Channels 1 and 2

 Balanced XLR Input for Channel 1, or for Bridged Mono

 2-Position Mode Switch - Enables Bridged Mono Mode

 12 Volt Trigger Input / Output Connector

AHB2


Quick Start Guide

Overview

 Connect all cables before turning the unit on.

 Check the settings of the

MODE

and

SENSITIVITY

switches before turning the unit on.

 Turn down the audio source before turning the unit on for the first time.

1. Set the MODE Switch

The

MODE

switch is very important, make sure it is set correctly for your application. An incorrect setting will not cause damage, but it may cause low output levels, a missing channel, or a polarity inversion.

The

AHB2

power amplifier can be run in two modes:



STEREO

mode - Two output channels



MONO

mode - One output channel in bridged mono

The bridged

MONO

mode will deliver almost 4 times as much power into an 8-Ohm speaker, and will do so without any increase in distortion. The

MONO

mode is an excellent choice for high-power applications. In

MONO

mode, two amplifiers will be required for stereo operation.

 Set this switch to

STEREO

if the

AHB2

is driving a stereo pair of speakers.


STEREO

if the

AHB2

is driving two channels of a multi-channel system.


STEREO

if the

AHB2

is driving a biamped two-way speaker.


MONO

if the

AHB2

is driving one speaker.

2. Set the SENSITIVITY Switch

The

SENSITIVITY

switch must be set properly in order to maximize the signal to noise ratio of your audio system. If this switch is set too low, you will not be able to drive the amplifier to its rated output. If this switch is set too high, the noise produced by your preamplifier will be amplified more than is necessary.

 If you are using an unbalanced input, you must use one of the top two switch positions.

 If you are using a balanced input, you will usually need to use one of the bottom two switch positions.

 Set this switch all the way down if you are using professional balanced sources.

 Raise the switch to increase the output level.

 Lower the switch to decrease the output level.

When set properly, you should be able to drive the amplifier to the onset of clipping when your volume control is set near maximum.

AHB2


3. Connect the Audio Inputs

There are two balanced XLR audio inputs on the

AHB2

:



1 IN/MONO IN



2 IN

Special adapter cables are required if balanced sources are not available. The adapter cables extend a three-wire balanced connection back to an unbalanced RCA output. The adapter cables are available from Benchmark.

 Use

1 IN/MONO IN

for the left channel of a stereo system.

 Use

2 IN

for the right channel of a stereo system.

 Use

1 IN/MONO IN

for all

MONO

mode applications.

Please note that unbalanced sources will limit the overall performance of the playback system. This is not due to any limitations in the

AHB2

. It is due to the noise limitations of unbalanced output drive stages. High-level balanced interconnects are required in low-noise systems.

We highly recommend balanced interconnects.

4. Connect the Speaker Outputs

The

AHB2

has twist-lock NL4 SpeakON connectors that provide very high-quality speaker connections. These connectors outperform most binding posts, have very low resistance, and are designed to reliably carry high current. These jacks are compatible with two-pole NL2 plugs or four pole NL4 plugs. For best performance, make all speaker connections using twist-lock SpeakON connectors. Binding posts are included to provide compatibility with existing speaker cables.

 Use

1+

and

1-

for the channel 1 output in

STEREO

mode.

 Use

2+

and

2-

for the channel 2 output in

STEREO

mode.

 Use

M+

and

M-

for the output in

MONO

mode.

The

1&2 OUT

NL4 jack provides access to channels 1 and 2. If an NL2 plug is inserted into this jack, it will have access to channel 1 only.

Use this jack with a two-pole cable to connect the channel 1 output to the left speaker in a stereo system.

The

2 OUT

NL4 jack provides access to channel 2 only.

Use this jack with a two-pole cable to connect the channel 2 output to the right speaker in a stereo system.

The

BRIDGED MONO OUT

NL4 jack provides a dedicated output for bridged mono applications.

Use this jack with a two-pole cable to connect the bridged output to a single speaker.

The

1&2 OUT

NL4 jack can also be used for biamp applications.

Use this jack with a four-pole cable to connect both output channels to the high and low drivers in a biamped 2-way speaker.

AHB2


5. Connect the AC Power Cord

The AC input connector accepts standard IEC input cables. Use a grounded cable that is appropriate for your location. The AC input is auto ranging and may be used internationally without changing any settings or fuse sizes. Fuses are located in a drawer at the top of the AC input connector.

6. Turn on the Power

 Turn down the audio source before turning the unit on for the first time.

 Press the POWER button to turn the unit on or off.

Note: Audio will automatically mute on startup and shutdown to protect the speakers and eliminate unwanted transients.

7. Check the Status Indicators

The amplifier has the following status indicators:



POWER

- Power-status indicator, On = Normal, Flashing = Fault



CLIP

(one per channel) - Audio-clip indicator, Flash = Clip, Off = Normal, On = Fault



TEMP

(one per channel) - Over-temperature/current indicator, Off = Normal, On = Fault



MUTE

(one per channel) - Channel-mute indicator, Off = Normal, On =

PROTECT

or

MUTE

POWER - Power Status Indicator

 Off = Power is Off

 On = Normal Operation

 Flash = Fault Condition, Power Supply has Shut Down,

PROTECT

CLIP - Audio Clipping Indicators

 Off = Normal

 Left or Right Flashing = Some Clipping is Occurring

 On = Fault Condition, Excessive Clipping has Occurred,

PROTECT

TEMP - Over-Temperature Indicators

 Off = Normal

 Left or Right Flashing = Peak-Current Warning

 Left or Right On and POWER On = Over-Current Fault,

PROTECT

 Left or Right On and POWER Flashing = Over-Temperature Fault,

PROTECT

 Both On = Other Fault Conditions,

PROTECT

MUTE - Audio Mute Indicators

 Off = Normal

 Both On During Start Up or Shut Down = Normal, Audio is Muted

 Both On =

PROTECT

or

MUTE

Mode, Audio is Muted

AHB2


Bidirectional 12 Volt Trigger

Benchmark has reinvented the 12 volt trigger by adding bidirectional signaling. The trigger connection on the

AHB2

can be used as an input, an output, or both. It is compatible with any common 12 volt trigger input or output. The

12V TRIGGER

can be used to turn the

AHB2

power amplifier on or off automatically in sequence with other audio system components. The

AHB2

can also turn other connected components on and off.

Linking Multiple Audio Components

Two or more

AHB2

power amplifiers can be linked together with

12V TRIGGER CABLES

, so that all units power up and down together. This group of amplifiers can be linked to a group of

Benchmark

DAC2

D/A converters. In such a system, any power button can be used to turn the system on or off.

Trigger Wiring

The

AHB2

has two bi-directional

12V TRIGGER I/O

jacks. These jacks are 1/8" (3.5 mm) TRS connectors. The tip is wired to the

12V TRIGGER I/O

bus. The sleeve is wired to chassis ground.

There is no connection to the ring.

Trigger Cables

The

AHB2

includes one 3-foot (1 m)

12V TRIGGER CABLE

. This cable has a 1/8" (3.5 mm) TRS connector at each end.

Automatic Power-Down Feature

40 Minute Timer

The

AHB2

has an audio signal presence detector on each input channel. If no audio is detected on either input for a period of 40 minutes, the

AHB2

will automatically shut down to save energy. This feature is required by law in many countries, and can contribute to significant energy savings.

This auto-off feature is programmable. Starting with the unit on, press and hold the POWER button for 7 seconds to toggle this feature (press and hold the POWER button until the MUTE lights turn off). This setting is stored in memory and is recalled when the unit is turned on.

Press and hold the power button for 1 second to view the status of this feature. If the timer is enabled, the TEMP lights will turn on while the POWER button is pressed.

Timer Deactivates the 12V TRIGGER

When the

AHB2

executes an automatic power down, it will pull the

12V TRIGGER

low to shut down any equipment attached to the trigger bus. The timer is only active when the system is started using the POWER button on the front of the

AHB2

.

AHB2


No Warm-Up Required

Unlike most power amplifiers, the

AHB2

reaches its full rated performance very quickly. Full rated performance is reached in less than one minute. For this reason, there is absolutely no reason to keep the

AHB2

powered on when not in use. The feed-forward error correction circuits in the

AHB2

keep it very stable over a wide range of operating temperatures.

AUTO-ON Feature

The

AHB2

has a programmable AUTO-ON feature. When this feature is enabled, the

AHB2

will automatically turn on whenever AC power is applied. The 40-minute timer is automatically disabled when this feature is activated. The POWER button will act as a MUTE button when this feature is enabled. When AUTO-ON is enabled, the POWER button will toggle MUTE on and off. In

MUTE

MODE

, the POWER light and MUTE lights are on, and all other lights are off.

To enable the AUTO-ON feature, start with the unit off. Then press and hold the POWER button for

3 seconds. The CLIP lights will turn on at the end of 3 seconds. Release the POWER button as soon as the CLIP lights turn on. Press the POWER button to verify that the AUTO-ON mode is enabled. If it is enabled, the POWER button will toggle MUTE on and off.

To disable the AUTO-ON feature, start with the unit on. Then press and hold the POWER button for

3 seconds. The clip lights will turn off at the end of 3 seconds. Release the Power button as soon as the CLIP lights turn off. The unit should now turn off (verifying that the feature has been disabled).

AHB2


Rack Mounting

The

AHB2

is available in a rack-mount version. The

AHB2

is magnetically shielded, and will not interfere with sensitive equipment mounted above or below the

AHB2

.

Rack Mount Option

Rack Mounting Instructions

The

AHB2

runs very cool when idle and runs very cool under most load conditions. However, it can produce significant heat when heavily loaded. Make sure the rack is adequately ventilated. Make sure the side heat sinks have an unobstructed air flow.

Some power amplifiers can emit very strong magnetic fields. These amplifiers should be kept at least two rack units above or below the

AHB2

. Magnetic interference can produce hum problems.

If the

AHB2

is mounted directly above another piece of equipment, it may be necessary to remove the feet from the

AHB2

. Save the feet for future needs. Replacement feet may be purchased directly from Benchmark or through most authorized Benchmark dealers.

AHB2


Fault Protection Circuitry

The

AHB2

is designed to detect overloads, short circuits, clipping, excessive temperatures, high

DC offsets, and low AC input voltages. When a potentially-damaging fault occurs, the amplifier enters a special "

PROTECT

" mode to prevent damage.

The amplifier has a comprehensive set of fault-detection circuits that will activate the

PROTECT

mode to protect against damage to the amplifier or speakers.

Fault-Detection Circuits

 Temperature sensor on each output channel

 Temperature sensor on main power supply

 Current sensor on each output channel

 Voltage clip detector on each output channel

 DC offset detector on each output channel

 SOA (safe operating area) detector on each output channel

 Load sensor on main power supply

 Fault sensors on all power supplies

 AC line under-voltage fault sensor on AC input

PROTECT Mode (Both MUTE Lights On)

In PROTECT mode, both MUTE lights are on. The CLIP, TEMP, and POWER lights identify the cause of the fault.

The

PROTECT

mode is only activated when a potentially damaging fault condition has occurred. To protect against damage, both audio outputs are muted. In some fault conditions, all high-power circuits are shut off. A small auxiliary power supply remains active so that the error condition can be displayed on the front panel.

If the

POWER

light is flashing, all high-power circuits have been shut down as an additional precaution.

If a fault has triggered the PROTECT mode, the amplifier must be turned off before normal operation can resume. Identify and correct the cause of the fault before restarting the amplifier.

AHB2


PROTECT Mode - Fault Codes

The following table provides a summary of all possible status display conditions. The

MUTE

lights will turn on and stay on whenever a fault condition has triggered the

PROTECT

mode.

If a fault has occurred, power must be turned off before normal operation can resume.

Identify and correct the cause of the fault before restarting the amplifier.

POWER CLIP TEMP MUTE MUTE TEMP CLIP Status

OFF OFF OFF OFF OFF OFF OFF Power off, or no AC input

ON

ON

ON

OFF

ON

OFF

ON

ON

ON

ON

ON

OFF

ON

OFF

AC Startup - lamp test

Mute on - startup or shutdown

ON

ON

ON

ON

OFF

FLASH

OFF

OFF

OFF

OFF

OFF

FLASH

OFF

OFF

OFF

OFF

OFF

OFF

OFF

OFF

OFF

OFF

OFF

OFF

OFF

OFF

OFF

Normal operation, no errors

Channel 1 - Clipping

FLASH Channel 2 - Clipping

Channel 1 - Current warning

ON OFF

FLASH ON

FLASH OFF

FLASH ON

ON

ON

OFF

OFF

ON OFF

FLASH OFF

FLASH OFF

FLASH ON

ON ON

OFF

OFF

OFF

OFF

ON

OFF

ON

ON

OFF

ON

ON

OFF OFF FLASH OFF Channel 2 - Current warning

ON ON OFF OFF Channel 1 - Clipping Fault

ON ON

ON ON

ON ON

ON ON

ON ON

ON ON

ON ON

ON ON

ON ON

OFF

OFF

OFF

ON

ON

OFF

ON

ON

ON

ON

ON

OFF

OFF

OFF

OFF

OFF

ON

ON

Channel 2 - Clipping Fault

Chan 1&2 - Clipping Fault

Channel 1 - Over-Current Fault

Channel 2 - Over-Current Fault

Chan 1&2 - Over-Current Fault

Channel 1 - Over Temperature

Channel 2 - Over Temperature

Power Supply Fault, Loss of AC

SOA Fault

AHB2


Clipping Fault

The input and output audio signals are compared to determine when clipping is occurring.

Occasional clipping will cause the

CLIP

lights to flash and will not trigger this fault. However, if a severe overdrive condition occurs, this fault is triggered to prevent damage to speakers. This fault indicates that the amplifier has been driven very hard into voltage clipping. Both channels are muted to protect the amplifier and speakers. A power reset will be required.

Fault Display:



POWER

light is Flashing

 Both

MUTE

lights are On

 One or both

CLIP

lights are On

 Both

TEMP

lights are Off

Typical Causes:

 The sensitivity switch may be set too high

 Output of preamplifier or DAC is too high

Required Actions:

 Check the position of the

SENSITIVITY

switch

 Move the sensitivity switch down one or two positions if necessary

 Turn down the audio source

 Restart the amplifier

AHB2


Over-Current Fault

The output current of each channel is constantly monitored. If either channel exceeds a safe output current, this fault is triggered and both channels are muted to protect the amplifier and speakers. A power reset will be required.

Fault Display:



POWER

light is On

 Both

MUTE

lights are On

 Both

CLIP

lights are Off

 One or both

TEMP

lights are On

Typical Causes:

 The load impedance of the speakers may be too low

 Speaker cables may be shorted


 Check for shorted speaker cables

 Make sure the nominal Stereo load impedance is 3 Ohms or higher

 Make sure the nominal Bridged Mono load impedance is 6 Ohms or higher



Speaker impedance always varies with frequency. Speaker impedance may be much lower than the rated "nominal" impedance at certain frequencies. The over-current fault detection circuits prevent potential damage that can be caused by driving very high signal levels into very low impedances.

In

STEREO

mode, at full output, the current limit can be reached if the load impedance dips below about 1.3 Ohms. In

MONO

mode, at full output, the current limit can be reached if the load impedance dips below about 2.6 Ohms.

AHB2


SOA Fault

The SOA (Safe Operating Area) of the output power devices is constantly monitored. If this safe operating area is violated, both channels are muted to protect the amplifier and speakers. A power reset will be required.

Fault Display:



POWER

light is On

 Both

MUTE

lights are On

 Both

CLIP

lights are On

 Both

TEMP

lights are On

Typical Causes:


 Speaker cables may be shorted

 Amplifier has been overloaded with a high-amplitude test tone


 Check for shorted speaker cables

 Make sure the nominal

STEREO

load impedance is 3 Ohms or higher

 Make sure the nominal Bridged

MONO




AHB2


Over-Temperature Fault

The temperature of the left and right heat sinks are constantly monitored. If either heat sink reaches the maximum allowable temperature, both channels are muted to protect the amplifier and speakers. All high-power subsystems are shut down to accelerate the cooling process. One or both heat sinks will be very hot. After the unit cools, a power reset will be required.

Fault Display:



POWER

light is Flashing

 Both

MUTE

lights are On

 Both

CLIP

lights are Off

 One

TEMP

light is On

Typical Causes:


 Heat sinks may be obstructed




STEREO



MONO


 Maintain adequate clearance around heat sinks

 Allow time for the amplifier to cool



AHB2


Power Supply Fault

The power supply has a number of sensors that monitor voltage, current, and temperature. If any parameter exceeds safe limits, both channels are muted to protect the amplifier and speakers. This fault may indicate that the AC power has been interrupted. It may also indicate that the power supply has overheated. It may also indicate the detection of an overload on one of the power supply rails. It may also indicate a fault condition in the power supply system. All high-power subsystems are shut down. A power reset will be required.

Fault Display:



POWER

light is Flashing

 Both

MUTE

lights are On

 Both

CLIP

lights are On

 Both

TEMP

lights are On

This fault display will only persist if AC is present.

In the event of a total loss of AC power, this error display will stay on for about 15-30 seconds and then all lights will turn off.

Typical Causes:

 The AC line voltage may have dropped below allowable limits for a few seconds

 AC power has been lost (if all lights turn off after about 15-30 seconds)


 Heat sinks may be obstructed



 Check the AC power source


STEREO



MONO


 Maintain adequate clearance around heat sinks

 If unit is hot, allow time to cool



AHB2


Specifications

Rated Output Power

1 kHz, < 0.00015% THD

 100 W/channel into 8 Ohms, both channels driven




 200 W Bridged Mono into 16 Ohms



Output Current

 29 A peak into 1 Ohm, both channels driven

Output Voltage

 > 80 Vpp into any rated load

Frequency Response

 Better than 0.1 Hz to 200 kHz, +0/-3 dB

 -0.01 dB at 20 Hz, -0.17 dB at 20 kHz, 8-Ohm Load

 -0.23 dB at 20 Hz, -0.32 dB at 20 kHz, 4-Ohm Load

Signal to Noise Ratio

 132 dB A-Weighted, Stereo Mode

 135 dB A-Weighted, Bridged Mono

 130 dB Unweighted, 20 Hz to 20 kHz, Stereo Mode

 133 dB Unweighted, 20 Hz to 20 kHz, Stereo Mode

Distortion

THD+N

 1 kHz, 80 kHz LPF, at full rated output into any rated load

 < -118 dB (< 0.00013%) - Stereo Mode

 < -118 dB (< 0.00013%) - Mono Mode

THD

1 kHz, 20 kHz LPF, at full rated output into any rated load

 < -119 dB (< 0.00011%) - Stereo Mode

 < -120 dB (< 0.00010%) - Mono Mode

AHB2


Crosstalk

 Better than -115 dB at 1 kHz

 Better than -92 dB at 20 kHz

Input Sensitivity

 Low-Gain = 22 dBu (9.8 Vrms)

 Mid-Gain = 14.2 dBu (4 Vrms)

 High-Gain = 8.2 dBu (2 Vrms)

 Use Mid-Gain or High-Gain settings for unbalanced inputs

 Unbalanced inputs require

RCA to XLRM adapter cables

Input Impedance

 50 k Ohms, normal mode

 1 M Ohm, common mode

Input CMRR

 80 dB at 20 Hz, typical

 80 dB at 1 kHz, typical

 65 dB at 20 kHz, typical

Trigger I/O

 12 VDC 200 mA current-limited output to trigger turn-on of remote devices

 DC input for slaving to remote devices

 Input responds to 3.3 V logic and higher, VIL = 1.26 V, VIH = 2.7 V

 Absolute maximum input voltage = 30 Vdc

 Absolute minimum input voltage = -0.3 Vdc

 Input Impedance = 20 k Ohms

 Two 1/8" (3.5 mm) TRS jacks

 Tip = 12 Volt Trigger I/O, Ring = no connection, Sleeve = chassis ground

Damping Factor

 350 at 20 Hz, 8-Ohms

 254 at 1 kHz, 8-Ohms



Environmental

 0° C to 50° C (32° F to 122° F) Ambient Temperature

 Up to 80% Humidity - Non-condensing

AHB2


Mechanical Drawings

Dimensions

AHB2


Rack-Mount Dimensions

AHB2


Performance Plots

Figure 1 – THD vs. Output Power - 4-Ohm Load

This plot shows the extraordinary THD performance of the

AHB2

. The feed-forward error correction circuits keep the output nearly distortion free.

The magenta curve is the output power. Power is shown on the right-hand vertical scale.

The green trace is the THD measured at the output of the left channel when loaded with 4-Ohms.

The red trace is the THD measured at the output of the right channel when loaded with 4-Ohms.

THD is shown on the left-hand scale.

The stair steps are caused by the THD within the AP2722. This stair stepping demonstrates that the

AHB2

is at or below the measurement limits of the AP2722 test set, even when the

AHB2

is driving a heavy load.

AHB2


Figure 2 – THD vs. Output Power - 8-Ohm Load

This plot shows the THD of the

AHB2

with an 8-Ohm load. Note that the results are almost identical to those shown in Figure 1 (with a 4-Ohm load). Together, these two plots demonstrate that the THD performance of the

AHB2

does not change with load.

AHB2


Figure 3 – THD vs. Output Power, Bridged Mono - 8-Ohm Load compared to No-Load

This plot also shows that the THD produced by the

AHB2

does not increase with loading. The red trace is the no-load THD performance in bridged mono mode. The green trace is the THD performance while driving an 8-Ohm load in bridged mono mode. Note that the

AHB2

shows no signs of increased distortion while delivering 397 W into 8-Ohms bridged mono.

AHB2


Audio Precision

400 dx=.979800 kHz dy=96.30 X/Y

01/13/15 09:10:15

300

X

/

Y

200

150

100

50

0

10 50 100 200 500 2k 5k

Hz

Sweep Trace Color

1 1 Red

Line Style

Solid

Thick

4

Data Axis Comment

Anlr.Ratio

Left

Cursor1 Cursor2

*350.4 X/Y *254.1 X/Y

Damping_Factor_8Ohm.at27

10k 20k 50k 100k 200k

Figure 4 – Damping Factor - 8-Ohm Load

This plot shows that the

AHB2

provides excellent damping to keep speakers tightly controlled.

AHB2


Figure 5 – FFT at 320W, 1 kHz, 8-Ohms Bridged Mono

This FFT plot shows the spectral purity of the

AHB2

. The green trace is the no-load performance.

The red trace is the performance at 320 W. Both are nearly identical. The 1 kHz fundamental has been removed with a notch filter to improve the resolution of the AP2722 test set. The 2nd harmonic measures -131.5 dB relative to the 1 kHz fundamental. The 3rd harmonic measures

-122.5 dB relative to the 1 kHz fundamental. The only other harmonic visible is the 5th and this measures about -139 dB relative to the fundamental.

AHB2


Regulatory Compliance

FCC and RoHS Compliance Statements

FCC Notice (U.S. Only)

NOTICE: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications.

However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures:

 Reorient or relocate receiving antenna.

 Increase the separation between the equipment and receiver.

 Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.

 Consult the dealer or an experienced radio/TV technician for help.

This device complies with Part 15 of the FCC rules. Operation is subject to the following two conditions:

1.

This device may not cause harmful interference.

2.

This device must accept any interference received including interference that may cause undesired operation.

Instructions to Users: This equipment complies with the requirements of FCC (Federal

Communication Commission) equipment provided that following conditions are met:

 RCA Digital Connections: Shielded 75-Ohm coaxial cable must be used.

NOTICE: Changes or modifications not expressly approved by the party responsible for compliance could void the user's authority to operate the equipment.

RoHS Compliant Information

This statement clarifies Benchmark Media Systems, Inc. product compliance with the

EU

’s

(European Union) directive 2002/95/EC, or,

RoHS

(Restrictions of Hazardous Substances).

As of July 01, 2006, All Benchmark Media Systems, Inc. products placed on the European Union market are

compliant

(containing quantity limit weight less than or equal to 0.1% (1000 ppm) of any homogeneous Lead (Pb), Mercury (Hg), Hexavalent Chromium (Cr VI), and flame retardant Polybrominated Biphenyls (PBB) or Polybrominated Diphenyl Ethers (PBDE)).

AHB2


CE Certificate of Conformity

AHB2


Safety

Product: Audio Amplifier, Audio Equipment, Stereo Audio Amplifier

Model: AHB2

Part Number: 500-18000-xx0

Parameters:

 Rated Input Voltage: 100-120 Vac; 220-240 Vac

 Rated Frequency: 50/60 Hz

 Rated Input Current: 8A

 Protection Class: I

Tested according to:

 CAN/CSA C22.2 60065/A1:2006

 UL 60065:2007

 EN60065/A12:2011

Certification Mark:

AHB2


Warranty Information

Benchmark 1-Year Warranty

The Benchmark 1-Year Warranty

Benchmark Media Systems, Inc. warrants its products to be free from defects in material and workmanship under normal use and service for a period

of one year from the date of delivery.

This warranty extends only to the original purchaser. This warranty does not apply to fuses, lamps, batteries, or any products or parts that have been subjected to misuse, neglect, accident, modification, or abnormal operating conditions.

In the event of failure of a product under this warranty, Benchmark Media Systems, Inc. will repair, at no charge, the product returned to its factory. Benchmark Media Systems, Inc. may, at its option, replace the product in lieu of repair. If the failure has been caused by misuse, neglect, accident, or, abnormal operating conditions, repairs will be billed at the normal shop rate. In such cases, an estimate will be submitted before work is started, if requested by the customer.

Attempts to deliberately deface, mutilate, or remove the product's label will render this warranty void. Benchmark will not honor warranties for any products disingenuously purchased on the US or Canadian markets for export.

The foregoing warranty is in lieu of all other warranties, expressed or implied, including but not limited to any implied warranty of merchantability, fitness or adequacy for any particular purpose or use. Benchmark Media Systems, Inc. shall not be liable for any special, incidental, or consequential damages, and reserves the right to change this information without notice.

This limited warranty gives the consumer-owner specific legal rights, and there may also be other rights that vary from state to state.

AHB2


Benchmark Extended Warranty Options

The Benchmark Extended 5-Year Warranty *

Benchmark Media Systems, Inc. optionally extends the standard 1-year warranty to a period of

five years from the date of delivery.

*For the extended warranty to become effective, the original purchaser must register the product at the time of purchase either by way of the enclosed registration card or through the product registration section of the Benchmark Media Systems, Inc. website. This optional warranty applies only to products purchased within the US and Canada and is extended only to the original purchaser.

Attempts to deliberately deface, mutilate, or remove the product's label will render this warranty void. Benchmark will not honor warranties for any products disingenuously purchased on the US or Canadian markets for export. The terms of the extended warranty are subject to change without notice. For products purchased outside the US and Canada, please refer to the

Extended Two 2-Year International Warranty.

The Benchmark Extended 2-Year International Warranty **

Benchmark Media Systems, Inc. optionally extends the standard 1-year warranty to a period of

two years from the date of delivery.

**For the extended warranty to become effective, the original purchaser must register the product at the time of purchase either by way of the enclosed registration card or through the product registration section of the Benchmark Media Systems, Inc. website. This optional warranty applies only to products purchased outside the US and Canada and is extended only to the original purchaser.

Attempts to deliberately deface, mutilate, or remove the product's label will render this warranty void. Benchmark will not honor warranties for any products disingenuously purchased on the US or Canadian markets for export. The terms of the extended warranty are subject to change without notice. For products purchased in within the US and Canada, please refer to the

Extended Five 5-Year Warranty.

Notes on Warranty Repairs

An RMA (return merchandise authorization) number, issued by our Customer Service

Department, is required when sending products for repair.

They must be shipped to Benchmark Media Systems prepaid and preferably in their original shipping carton with the RMA number clearly visible on the exterior of the packaging. A letter should be included giving full details of the difficulty.

AHB2


Consignes de Sécurité Importantes (French)

Symboles de Sécurité

Ce symbole avertit l'utilisateur d'importantes instructions de fonctionnement et d'entretien dans la documentation accompagnant cet appareil.

Ce symbole avertit l'utilisateur de la présence de tensions isolées à l'intérieur de l'unité qui peuvent provoquer des chocs électriques dangereux.

Ce symbole avertit l'utilisateur de la présence de tensions sur les connecteurs de sortie qui peuvent causer des chocs électriques dangereux.

Ce symbole avertit l' utilisateur que le produit ne peut être utilisé en toute sécurité à des altitudes inférieures à 2000 mètres.

Ce symbole avertit l' utilisateur que le produit ne peut être utilisé en toute sécurité dans les climats non tropicaux.

AHB2


Mesures de Sécurité

1.

Lisez ces instructions.

2.

Conservez ces instructions.

3.

Respectez tous les avertissements.

4.

N'utilisez-pas cet appareil près de l'eau.

5.

Ne pulvérisez-pas un liquide sur une surface quelconque, car cela pourrait provoquer une situation dangereuse. Nettoyez-le uniquement avec un chiffon humide.

6.

Ce dispositif génère de la chaleur lorsqu'il fonctionne normalement. Opérez dans un endroit bien ventilé. Ne bloquez-pas les ailettes du dissipateur de chaleur situées de chaque côté de l'appareil. Celles-ci émettent de la chaleur et doivent être bien ventilées.

7.

N'installez-pas l'appareil à proximité de sources de chaleur telles que des radiateurs, registres de chaleur, poêles ou autres appareils produisant de la chaleur.

8.

Utilisez uniquement avec des pièces jointes et des accessoires spécifiés par le fabricant.

9.

Utilisez seulement avec un stand, support ou une table conçue pour supporter le poids de l'appareil. Assurez-vous que des blessures ou des dommages ne se traduiront pas par des câbles tirés sur l'appareil ou son montage.

10.

Les sorties haut-parleurs sont capables de produire des tensions dangereuses. Utilisez des connexions de haut-parleurs isolées. Débranchez l'appareil avant de modifier les connexions de sortie de haut-parleur.

11.

Confiez toute réparation à un personnel qualifié. Il n'y a pas de pièce réparable par l'utilisateur

à l'intérieur de l'appareil. Il y a des tensions élevées exposées à l'intérieur de l'unité et celles-ci peuvent persister après que l'appareil est débranché. Ne tentez pas d'ouvrir l'un des couvercles, et ne retirez-pas les attaches. L'ouverture de l'unité annulera la garantie.

12.

Certaines pièces sont liées à la sécurité, ou sont tenues de respecter certaines règles. Toutes les pièces doivent être remplacées par des remplacements exacts sauf autorisation écrite accordée par référence. Les substitutions et modifications non autorisées peuvent créer des conditions de fonctionnement dangereuses ou non conformes qui annuleront la garantie. Les modifications non autorisées peuvent entraîner des risques d'incendie et d'électrocution. Toute modification non autorisée peut entraîner l'appareil à émettre des ondes excessive et les interférences magnétiques. Des modifications peuvent réduire l'immunité aux perturbations extérieures. Ne faites appel un personnel qui offrent des services de modification de produit.

AHB2


13.

Le cordon du CA est amovible. Utilisez un cordon 3 broches mis à la terre approprié à votre région. Votre revendeur peut vous fournir le cordon correct.

14.

Ne pas oublier le but de la prise de courant mise à la terre. La prise de terre est fournie pour votre sécurité. Quand une prise 3 broches n'est pas disponible, veuillez consulter un électricien pour remplacer la prise obsolète. Ne pas utiliser d'adaptateurs 2 broches vers 3 broches. Ne pas tenter de résoudre les problèmes de bruissement en soulevant sécurité terre du CA !

15.

Débranchez cet appareil pendant les orages ou si vous le laissez inutilisé pendant de longues périodes de temps.

16.

Cet appareil est équipé d'une alimentation intégrée auto-adaptable. Il n'y a pas de commutateur de sélection de tension interne - ne tentez pas d'ouvrir l'appareil. Les gammes de tension de fonctionnement vont de 100 à 120 Vac +/- 10%, et de 220 à 240 Vac +/- 10%. La fréquence de fonctionnement est de 50 à 60 Hz. Toutes les tensions d'exploitation utilisent le même type de fusible.

17.

Pour une protection anti-feu et anti-chocs continue remplacez toujours les fusibles avec la bonne taille et le bon type (T 8A H 250V, 5x20mm), (T = temps de retard, 8A = huit ampères,

H = haut pouvoir de coupure, 250V = tension nominale, 5x20mm = taille de la cartouche). .

Les fusibles ultrarupture utilisent un corps en céramique. Utilisez Bel Fuse 5HT 8-R, ou Schurter

0001.2513, ou un modèle exactement équivalent. Le porte-fusible comprend deux fusibles.

Toujours remplacer les deux fusibles en même temps.

18.

Ce produit ne peut être utilisé en toute sécurité à des altitudes inférieures à 2000 mètres.

19.

Ce produit ne peut être utilisé en toute sécurité dans les climats non tropicaux.

AHB2


Appendix

A Radical Approach to Power Amplification

The performance of the

AHB2

would not have been achievable without taking a radical approach to power amplification. In many ways, the

AHB2

is a complete 180 degree departure from traditional high-end amplifier designs.



AHB™ Amplifier –

This unique amplifier uses THX-patented AAA(TM) (Achromatic Audio

Amplifier) technology to achieve high efficiency and vanishingly low distortion. The AHB2 combines class-H, and class-AB amplifier technologies with feed-forward error correction.



Feed-Forward Error Correction -

Each channel of the

AHB2

is equipped with a main amplifier and an ultra-clean low-power auxiliary error-correction amplifier. The main class-

AB amplifier provides the bulk of the power while the auxiliary amplifier provides a lowpower error-correction signal. These amplifiers are combined to create a near-perfect null of all distortion components. The

AHB2's

patented feed-forward error-correction system is much more effective than traditional feedback error-correction systems. Distortion does not change with loading, and does not rise near maximum output. Difficult loads are driven with near-perfect clarity. Low-level musical details are delivered without the masking effects of crossover distortion. The

AHB2

is virtually distortion free at low levels, at maximum output, and everywhere in between. Overall, the distortion produced by the

AHB2

is so low, that it approaches or exceeds the measurement limits of some of the finest audio test systems.



Error-Correction Amplifier -

The error-correction amplifier is a small ultra-clean amplifier that feeds a correction signal forward to the main output. The correction amplifier actively drives the output while the main output devices are transitioning between push and pull states. The correction amplifier actively suppresses distortion products that would normally occur in a class-AB output stage. This feed-forward system is much more effective than traditional feedback networks. Feedback systems attempt to correct errors after they happen. In contrast, feed-forward systems can prevent errors from occurring.



Low-Bias Class-AB Main Amplifier -

Class-AB output stages always produce "crossover distortion" whenever the push-pull output drivers change state. Precise bias control is usually required to minimize this crossover distortion. Traditional feedback networks have difficulty correcting the transients caused by push-pull crossover transitions. However, the

THX patented feed-forward error-correction system has the speed and precision necessary to virtually eliminate all traces of crossover distortion. With this feed-forward system, bias currents have no significant impact on the distortion at the output of the amplifier. This topology provides the freedom to conserve power by setting unusually low bias currents.

The

AHB2

uses very low bias currents but achieves vanishingly low distortion - even under heavy loading.



Class-H Tracking Rails -

Multiple power supply rails (class-G), and tracking power supply rails (class-H), can improve the efficiency of a class-AB amplifier. The

AHB2

uses a lower fixed rail and an upper class-H tracking rail. The improved efficiency provided by this topology usually comes at the cost of increased distortion. For this reason, there are very few amplifiers that use multiple supply rails. In a traditional feedback design, every rail switch point adds another layer of crossover distortion. In contrast, the feed-forward error correction used in the

AHB2

is so effective that multiple rails can be added without incurring any distortion penalty.

AHB2




Low Gain –

The

AHB2

has a low gain setting that optimizes the gain structure of professional monitoring systems. Maximum rated output is reached at an input signal level of 22 dBu. This places the upstream equipment in an ideal operating range to maximize the

SNR of the monitoring chain. Most power amplifiers have far too much gain, and this degrades noise performance of the overall system. To provide compatibility with lower input signal levels, the

AHB2

has an ultra low-noise input amplifier with a 3-prosition gain switch.

The upper two settings boost the gain to allow direct interfacing with Hi-Fi components that typically operate at lower signal levels than those produced by professional components.



Passive Cooling –

The sonic performance of the

AHB2

would be impossible to appreciate if it had a motor-driven fan. There are no noise-generating fans to detract from the total silence of the

AHB2

. Experience every detail of your favorite recordings without the masking effects of fan noise.



Resonant Switch-Mode Power Supply –

Most high-end power amplifiers use unregulated linear power supplies. The conventional wisdom is that linear supplies are electrically quieter than switching supplies. Benchmark's research shows that this is a myth. Linear supplies have transformers that operate at the AC mains frequency. The problem with these 50 to 60

Hz transformers is that they must be very large in order to supply the required power.

These large low-frequency transformers generate large stray magnetic fields that can interfere with other nearby devices, and with the amplifier itself. The noise performance of many traditional power amplifiers is limited by the amplitude of the AC line-related hum.

This hum is often magnetically induced and is very hard to eliminate. To solve these problems, Benchmark now uses switching power supplies in all of its newer products.

Switching frequencies are set well above the audio band. More importantly, the high switching frequency greatly reduces the size of the magnetic components and the magnitude of the stray magnetic fields. Resonant switching is used in the

AHB2

to minimize switching noise. Resonant supplies switch at low voltage and low current and are much quieter than traditional switching supplies.



Regulated Power Supply -

Audio amplifiers usually use unregulated supplies. The theory is that the amplifier can produce higher peak output power for a given power supply size.

Linear regulation would throw away power that could be delivered to the output devices.

Benchmark's move to switching supplies changes the efficiency equations. Switching supplies can produce a regulated output without wasting power and without creating unwanted heat. A further advantage of regulation is that the output voltage is not a function of AC line voltage, prior audio content, or speaker loading. The switching supply in the

AHB2

responds to bass frequencies, maintains a constant low-ripple output voltage, and delivers very predictable output power.



Low Stored Energy -

Most audio power amplifiers rely on a bank of large capacitors for energy storage. These capacitors remove some of the ripple produced by an unregulated linear supply, and help reduce supply sag in order to maintain a high output level immediately following musical peaks. Unfortunately, these capacitors also slow down the recovery from voltage sag due to peak loading. Benchmark's approach is to nearly eliminate all storage after the power supply. The power supply regulation takes the place of energy storage, responds quickly to peak loading, maintains very low ripple voltage, and provides immunity to AC line-voltage fluctuations.



Digital Protection Systems -

The

AHB2

has a digital control system that monitors all of the critical functions in order to provide comprehensive protection from overload and fault conditions. Many of these systems do not exist in traditional designs.

AHB2




NL4 SpeakON Output Jacks -

SpeakON connectors are well-accepted in high-power proaudio applications, but are nearly unknown in high-end Hi-Fi applications. Our tests show that these robust connectors provide a much more reliable connection than the binding posts, spade lugs, pins, and banana plugs used with traditional Hi-Fi amplifiers. Distortion is measurably lower when using NL4 connectors. These connectors provide a very reliable, low-impedance connection. Furthermore, they are polarized and fully insulated to protect against short circuits, polarity reversals, and shock hazards. Benchmark recognizes that the

Hi-Fi industry is slow to embrace new ideas, so we have provided traditional binding posts wired in parallel to the NL4 jacks. But, for the highest performance, we recommend using the NL4 jacks. The jacks accept NL4 or NL2 plugs.

In summary, Benchmark has taken a radical approach to audio amplification, has leveraged patented technologies (licensed from THX Ltd.), and has reversed many common practices. The result is an amplifier that is significantly quieter, cleaner, smaller, and more efficient than any traditional design. There is nothing ordinary about the Benchmark

AHB2

.

AHB2


Copyright © 2014

Benchmark Media Systems, Inc.

All rights reserved.

Benchmark Media Systems, Inc.

203 East Hampton Place, STE 2

Syracuse, NY 13206-1633

USA

PHONE: +1-315-437-6300

FAX: +1-315-437-8119 www.benchmarkmedia.com

AHB2


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